1. Field of the Invention
The present invention relates to a slip gear structure and a timepiece equipped with the same.
2. Description of the Related Art
There has conventionally been known a slip gear structure in which a shaft and a gear main body are slip-engaged with each other so that they may rotate integrally during normal operation and that when the load applied between the shaft and the gear increases to a degree not less than a certain level, slippage may be generated between the shaft and the gear; it is applied, for example, to a winding mark wheel of a power reserve mechanism (winding mark mechanism), and a wheel related to time correction, etc. of a chronograph timepiece or the like.
In such a slip gear, there is typically adopted a swaging structure called cannon pinion crushing (See, for example, JP-A-2000-98056).
However, this swaging structure not only requires a sufficient wall thickness for swaging, but involves generation of play when dismantling and assembly are repeated, resulting in the loss of slip engagement.
As a slip gear, there is also known one in which a gear main body is engaged with a shaft by an arm-like spring (See, for example, JP-A-11-183652).
However, in this type of slip gear using an arm-like spring, there is no appropriate portion to be retained (grabbed) at the time of dismantling/assembly, so that there is a fear of breakage at the time of dismantling/assembly, which means, this type of slip gear is not suited for application to a portion where dismantling/assembly is conducted (e.g., where gears are arranged coaxially on both main surface sides of a support substrate such as a main plate.